This invention relates to devices for reducing back pressure in internal combustion engines, and more particularly relates to an exhaust gas back pressure reducer which can be attached to the exhaust pipe.
Because of the overlap condition in internal combustion engines during which intake and exhaust valves are open simultaneously for a short period, back pressure can considerably reduce efficiency. For this reason, a number of methods and devices have been provided in an attempt to reduce the exhaust back pressure. In some cases this is accomplished by separate individual exhaust pipes connected directly to the exhaust manifold for each cylinder. This is one method used in aircraft engines or internal combustion engines used in racing cars. However, this type of method does not permit any type of muffler to be used for the reduction of noise. In vehicles, such as passenger cars, used for public transportation, noise reduction is important, and therefore, mufflers must be installed which increase the length of the exhaust system and necessitate the installation of a single exhaust manifold. This, however, because of the interconnected exhaust manifold and length of exhaust pipe necessary for insulation of a muffler, increases the possibility of back pressures. Some devices for reducing exhaust gas pressure have attempted to accomplish this by scooping air into the tailpipe or exhaust conduit and mixing this air with the exhaust gases inside the tailpipe. These devices are dependent for their effectiveness upon the velocity of the air injected directly into the exhaust conduit. They effectively succeed only in offsetting any accomplished pressure reduction by increasing the pressure in the exhaust system in amount equal to or greater than the original reduction which was hoped for. Air scoops externally of the exhaust pipe have been tried, but accomplish nothing more than a mere diffusion of the exhaust gases with air at emission from the tailpipe or into exhaust conduit.